Description of the Prior Art
This invention, in its preferred form, relates to apparatus for interrogating a plurality of remote stations over available data network channels such as ordinary telephone lines, to obtain data as provided by a plurality of transponders disposed at corresponding ones of the remote stations. Typically, each of such transponders is associated with a plurality of data sources such as utility meters in the form of gas, water or electric meters.
Data accumulating systems for accessing utility meters utilizing conventional telephone lines, are well known in the art as exemplified by U.S. Pat. Nos. 3,400,378 of Smith et al.; 3,700,816 of Evans et al.; and 3,786,423 and 3,868,640 of Binnie et al. Typically in such systems, an interrogating signal is sent from the central station to a remote station, whereat the transponder is disposed to receive the interrogation signal, to access a selected utility meter, and thereafter, to transmit a return signal with data indicative of the utility consumed to the central station. The returned data indicative of the utility consumed may then be used for billing purposes. Thus, it is apparent that by utilizing the telephone lines to access data generated by utility meters, utility companies may avoid the expense of sending meter readers to the remote stations such as individual residences to read the meter and to record the utility consumed data by hand, whereby bills may be sent to the utility customers.
In the particular system described in U.S. Pat. No. 3,868,640 of Binnie et al., there is included a plurality of remote stations each including meters for registering the use of such utilities such as gas, electricity, water and/or oil. An interrogating system disposed at a central station employs a computer to transmit interrogation signals over the telephone lines to selectively access one of the remote stations. The addressed remote station responds to the interrogation signal to read the outputs of one or more of its meters. The remote station responds to the interrogation message by generating and transmiting a return signal indicative of the utility consumed of each of its meters, to the interrogating system disposed at the central station. Noting that the centrally disposed interrogating system employs a computer, such computer can be used to receive and use the utility consumed return message to compute bills for each of the customers associated with the remote stations.
The prior art has been long aware of the problems of generating sufficient electrical power at critical or peak times. One suggested solution is to encourage customer consumption of electricity at other than the critical or peak hours by employing a utility rate that charges premium prices for electricity consumed at the peak hours. The prior art has taught the use of mechanical peak demand meters, which measure the peak utility consumed to be mechanically stored and read out at a later period of time.
The prior art as exemplified by U.S. Pat. Nos. 3,747,068 of Bruner et al., 4,086,434 of Bocchi et al. and U.S. Pat. No. 4,213,119 of Ward et al. illustrate efforts to use electronic, automated interrogating systems as described above to access remote locations in a manner whereby an indication of the utility consumed at different periods of time may be sensed and transmitted back to the centrally disposed station to provide a computation of utility consumption costs based upon a variable rate schedule. A common element to each of these systems is the use of a clock at each remote station to determine the time of day and to facilitate the recording of utility consumed as a function of the time of day.
U.S. Pat. No. 3,747,068 of Bruner et al. discloses a remote meter reading system adapted to take continuous meter readings of a meter disposed at a remote station, including a transponder responsive to an interrogation signal occurring at irregular times to provide data indicative of the total accumulated consumption of utility as measured by the meter over a fixed period of time as well as an indication of the maximum utility consumed within a defined interval of that period of time. Due to the irregular interrogation of the remote meter reading system, it is desired to know the maximum or demand utility consumed for the last full time period regardless of the irregularity of interrogation. To this end, Bruner et al. discloses a demand meter supplying pulses indicative of the utility consumed to a first or demand counter that is reset each fifteen minutes by a demand clock generator. A comparator and storage circuit compares the pulse count indicative of the utility consumed in the last defined interval as stored in the counter with the previous maximum utility for a fifteen minute interval and if the current count is greater, that count is transferred to and stored in the storage circuit. At the end of a time period, e.g. one month, the demand clock generator provides a transfer signal to transfer the demand or maximum count from the comparator and storage circuit to a first of two accumulators. At the end of each fifteen minute interval, the demand clock generator applies an actuating signal to the comparator and storage circuit, whereby the comparison between the count total during the last interval and the maximum count as stored in the circuit is made. At the end of the next time period, e.g. one month, a pulse is applied to the second accumulator, whereby the maximum utility consumed within the fifteen minute interval during the second time period is stored in the other accumulator. Upon interrogation, a message including an address as derived from an address multiplexer indicative of the particular demand meter interrogated and the values as stored within each of the first and second accumulators, is transmitted via the output transponder to the interrogation unit. By evaluation of the counts as stored in the storage circuit and those in the accumulators, the maximum utility consumed for a fifteen minute interval of the last time period may be determined in accordance with a set of rules.
U.S. Pat. No. 4,086,434 of Bocchi discloses a remote condition (meter) reporting system employing a microprocessor and a calendar clock circuit operative to interrogate a plurality of meters including a gas, water or electric meter as connected to a latch. The clock circuit is generally used to provide timing signals whereby the microprocessor can initiate telephone calls to a central location and significantly, to accumulate pulses from the meters over a given period of time. Further, a battery as charged from a standard 60 cycle house current line is used to provide power to each of the components including the microprocessor, whereby the system continues to be energized in the event of an electrical power outage. The calendar clock circuit provides timing signals indicative of the time of day and the day of month for reporting purposes. However, the clock is connected to a 60 cycle house current as a timing reference, whereby if the primary, power supply, i.e., the 60 cycle house current, fails, the clock circuit likewise will stop keeping time.
U.S. Pat. No. 4,213,119 of Ward et al. discloses a remote meter reading system, wherein a mobile remote unit is adapted to interrogate by the use of a laser beam a utility meter coupled to a monitor unit and to a transponder. In operation, an interrogator beam is transmitted from the remote unit to the transponder and the monitor unit, which in turn interrogates the utility meter to determine the quantity of measured utility. The monitor unit in turn transmits a data radiation pulse train that is detected by a receiver unit, the detected data to be stored in a data storage unit. The data storage unit includes a multiple memory monitor unit, wherein there is included a plurality of storage and readout units, each connected by an optical monitor to a utility meter. Upon receipt of an interrogation pulse, each of the storage and readout units is sequentially interrogated and a train of pulses is applied to a laser data transmitter, which in turn generates a plurality of data laser pulses. A "time of day bracketing circuitry" is disclosed as including a plurality of counters, each dedicated to count pulses corresponding to consumption of a unit of measured utility for a particular time period. A clock signal is applied to an "N countdown counter" whose output is in turn applied to a "time bracket selector" which provides three outputs to selectively enable one of the corresponding gates, whereby the count as derived from the meter scanner may be selectively applied to one of the counters. In a particular embodiment, a first counter stores utility consumption occurring daily between 1200 and 2000 hours of the day, a second counter stores utility consumption occurring between 2000 and 0400 hours and a third counter stores consumption between 0400 and 1200 hours. In this manner, a variable price rate is established for the consumption of utility in each of these three time periods during a 24 hour day. Further, a digital circuit for obtaining the maximum count or utility consumed during any test interval within a billing period is disclosed; for example, this digital circuit provides the maximum count during any fifteen minute interval within a 24 hour day. To this end, a clock is applied to a divide by N circuit to provide an output pulse for each fifteen minute interval. The meter output pulses are applied to a current buffer counter for each fifteen interval, and at the end of an interval are compared by a comparator to the number of meter pulses as previously stored in a peak storage register. If the pulse count of the peak storage register is greater than that stored in the current buffer counter, the comparator enables a transfer of the pulses stored in the current buffer counter to the peak storage register.
The above described remote meter reading systems employ a time of day clock to enable the selective storing of pulses indicative of utility consumed into discrete counters each dedicated to a particular time period. However, none of these patents makes provision for failure of the primary power source, e.g., the AC power lines. In the case of such failure, no provision is made to provide an ongoing indication of the present, accurate time of day. As a result, if there is a power failure, there is no assurance of an accurate measurement of the utility consumed during a particular period. For example, if upon return of power, the remote meter reading system is again energized, it is necessary to again reset the time of day clock of that system and to disregard the stored indications of utility consumed in that there is no assurance that there was an accurate indication of time of day whereby the measurements of utility could be properly attributed to a particular time period.
The prior art and in particular U.S. Pat. No. 3,820,073 of Vercellotti et al. has dealt with the problems associated with meter reading systems due to power failure. Typical of the prior art, Vercellotti et al. describe a remote meter reading system wherein upon restoration of power after failure, a binary non-volatile counter in which the accumulation of a utility is stored, is reset in a manner to accurately reflect its condition at the time of power failure. In another approach, U.S. Pat. No. 3,786,423 of Martell describes a remote meter reading system having a plurality of counters each associated with a meter for receiving its output pulses to be stored therein, and an auxiliary power supply in the form of a battery associated with the counters or accumulators to prevent count loss upon primary power failure. However, the aforedescribed prior art does not deal with the problem of restoring the time of day clock to the present time after restoration of power. Thus, if there is a power failure or interruption, the measurements accumulated in a remote meter reader system may not accurately reflect the power consumed during a particular time interval and the bills based upon a variable rate structure dependent upon time would be in error.